It is known to inflate an inflatable vehicle occupant protection device to help protect a vehicle occupant in the event of a vehicle collision. One particular type of inflatable vehicle occupant protection device is an inflatable curtain. Inflatable curtains inflate away from the roof of the vehicle downward inside the passenger compartment between a vehicle occupant and the side structure of the vehicle in the event of a side impact, a rollover, or both. A known inflatable curtain is inflated from a deflated condition by inflation fluid directed to the inflatable curtain from an inflator.